This is a special room. Hello -- Hernandez in New York -- -- ABC news digital special report double 07 out of the shadows for the first time ever. The head of Britain's top three intelligence agencies appeared together before parliament and before cameras. This morning the UK government wants answers for the damaging spying revelations by an -- -- Edwards Snowden. But the British intelligence services say they have also been trying to be more open. It's similar allegations that the NSA is facing here -- -- and it's got folks in Britain wandering -- they're being spied on. So -- won't -- the rules side threat come from. GC HQ. Not just from others. Seeking to collect everyone's data and communications. -- you. Why did you think it is mystery to collect information on the majority. Of the public. In order to protect us from the minority of potential even evildoers. It looks like what that a man. -- -- Just a tough fight but things we do not spend our time. Listening to the telephone calls or reading the emails of the majority of the vast majority that would not be -- would not be legal we do not do it. It would be very nice if terrorists or serious criminals use that particular method of communication. And everybody else -- something else that is not the case. It will be very nice if we knew who all the terrorists -- serious criminals live the instead as a set and yet. As a great way to two Norma mines and avoid identification. Today's proceedings it would bring in ABCs through the -- in London hello Brunell. What particular politicians have prompted the UK government to bring these men -- front of the committee. Well -- there's not so much of a bit of a revelation as a person -- -- with Snowden he is the precipitation for this. And his revelations about the extent of spying by the NS and the United States but also. About activities by -- British Secret Service -- in country. Have also instigated an investigation -- intelligence security committee -- of parliament. F folks in the US would probably only remember are recognized rather MI six because we -- know about James Bond. But what would the US equivalent to these three organizations it. Well firstly I'm the -- on James Bond Ian such a gentleman but very important MI five who the closest equivalent in the US of the the FBI and perhaps it's not Department of Homeland Security -- that I -- by the broader remit. M -- six would be the CIA. And GC HQ would be the NSA. TC HQ what does that stand for. -- could not tallies. It's that -- secretive -- day. You know this -- extremely unusual situation that in the past UK's even denied the existence of some of these organizations now there. Front and center in public in front of cameras. Yes -- is apps that are unprecedented and -- if caught all of a desire. The bodies -- -- nations to be more transparent -- that actually didn't give much away and partly that walls. Even in the context of this of these -- to -- -- -- discussions. There was a two minute delay for that's estimate just in case they inadvertently -- left the state secret -- -- -- of this is quite sanitized. When there may -- as such and that. That the level is about as is necessary to fool -- they also -- specific examples of we're told that they couldn't speak about that in public that this would be this intellectually giving them off camera. And later on today. Are still a lot of a lot of sensitivity about some of the things being discussed. Absolutely foreign heads of state of an upset with the US for spying on them. Given some of these new or revelations is that in the case with the UK agencies as. -- Him well. It's it's a bit ambiguous the question is whether or not a Britain actually helped. I'm America spy on some of that allies whether that some some complicity that -- cooperation. There's been some questions about some -- that is after acquittal on the top of the US you can have this in done in. But we are cells apparently I'll definitely not being spied upon. And this is also -- -- -- four have been attention that I European allies that our relationship is perceived is and will be rightfully in this context is different from from that as of America. -- catering who -- dip in for a moment because it looks like there's testimony. I'm sure we can all very happily endorse what you have just said. I'd be grateful to -- -- could remain seated for a moment while our witnesses lead. I political decision -- -- report four. OK so there's an example of what we've been talking about a period of time where there's something. Sensitive about to be discussed and -- clear the room. Yes and -- it's -- quite. Ben -- in -- way I'm it is not I think the first pro America really is setting you'd expect a slightly more combative. Environments as a bit more adversarial but as you can see it's holding quite polite. And quite genteel in a rather -- And British sort of way -- -- and it. There -- some interesting parts of the hearing and what -- been dealt with so called terrorist tourism and analysts in the back. We're talking about -- tourist. Is that your assessment of the past his impending threat or decreasing. It's grown recently and is growing at the moment because of Syria. Syria has become a very attractive place for people to go for that reason those -- So political sympathize win the al-Qaeda ideological message that I mentioned. We've seen low hundreds -- People from this country go to Syria for periods and come back. Some large numbers still bad and get involved in fighting and this is partly because of the proximity -- Syria and the ease of travel. But also because it's attractive. What they would see -- -- -- Heidi Cole was. Idea hundreds of people traveling be part of terrorist groups is -- an alarming figure. Yes I think it is a -- and I I think is alarming not just in theory but in practice because what we've seen. Where it attacks. It all on the UK the 77 bombing on the 2005 was weasel you know that was it's -- doesn't -- the those people web radicalized by visits to Pakistan hardly a country in the state of war but which had training camps. It's the thought of people in Syria which is an active conflict -- as we know extreme Tea Party groups in operation. -- -- -- -- gonna have tried and tested techniques methodologies imbued in them an actual battlefield experiences. I think there's a very real danger about this that the -- that people will come back. With the skills to actually implement. Radical Jihad type policies also people may go out their own in a sense pursuing a worthy -- they sit and become radicalized -- -- environment as well. And before you go let's play one more clip this one about the relationship between the UK and the US we'll get your reaction. It is if it was an allegation. That you see your and relationships me then that the nexus is innocent and the potential reasoning -- not well founded. I think it's really important that we are clear that the public comments can you give -- a guarantee today. That you do -- who does operations. Which this week. That -- -- legal fight. Yes I can give you that. Guarantee. -- believe that it's true we are subject to -- -- and -- -- say I'm sure that's true my sister agencies as well. I -- the US and the UK have historically. Shared a strong relationship in terms of intelligence but is there now the sense that we're tainting the British and -- ethics. I -- -- I think British and American security agencies work very closely together. And have. A very close working and trusting relationship and if any place where the -- center all the special relationship. The circles special relationship between the US in the UK it is exactly in those areas so I don't think it's -- it I think you might. Notice the use the word I believe we -- contributing I mean this caveats there are plenty as well. So lomb in -- remains is seen as we get on the line whether or not there any more revelations about what's actually being done but I do not think. That it's this. The Snowden controversy has affected the relationship in any way in many ways -- clarify the extent to which Britain. And America actually work hand in hand and have very similar objectives and pursuing the same soul all of conceived threats. -- it will bring -- rover -- thank you for. Sharing with us and helping us understand is rare looked at British intelligence and how things are done and your side of the pond. Pretty -- and the London bureau and you've been watching ABC news digital special report on -- Hernandez in New York.

This transcript has been automatically generated and may not be 100% accurate.

Now Playing: Pictures Taken Around the World Capture the Elusive Blue Moon

Now Playing: Big Game Hunter Who Shot Lion Faces Scrutiny

Now Playing: The Government of Zimbabwe Seeks to Extradite Dr. Walter Palmer

{"id":20817295,"title":"UK Government Holds Hearings on New Spying Allegations","duration":"9:17","description":"British officials testify over new allegations of spying following alleged leak from Edward Snowden.","url":"/International/video/edward-snowden-update-uk-government-holds-hearings-spying-20817295","section":"International","mediaType":"Default"}